The only thing that can be done is have fewer children. Everything else is rearranging the deck chairs on the Titanic.
The good news is that this is already happening in most places. The bad news is that population growth is still out of control in Africa and parts of Asia, and may lead to a environmental crisis before population growth gets under control.
And yet, those places in Asia and Africa are much less of a problem for the environment than we are in Europe and the USA.
Raw population numbers are not the biggest concern. Consumption and excessive luxury, wasteful production practices and burying all of these under the rug are the root of all these problems
And as it turns out, it's your childhood friend that get to raise those children and not you, so if you wanted to help posterity then we'll have to hope your friend isn't a climate change denier or something.
The good news is that this is already happening in most places. The bad news is that population growth is still out of control in Africa and parts of Asia, and may lead to a environmental crisis before population growth gets under control.